On some devices, there is a need to bias a rotatable object toward a predetermined position on its rotational axis. For example, some aircraft flight control systems utilize a gimbal assembly to translate any movements of a flight control stick into the rotation of a plurality of shafts about two rotational axes. These shafts may be biased to a predetermined position to enable the flight control stick to return to a null position when it is released by the pilot or co-pilot.
In this passive mode, a force is required to release the object from the predetermined position, providing physical feedback to the user of the object and indicating to the user that the mechanism is in the predetermined position. Thus, the control stick that is coupled to a gimbal assembly may be releasably secured in its null position by securing each of the shafts in a predetermined position about its axis of rotation, and preventing the control stick from moving unless the pilot or co-pilot applies enough force to allow rotation of one or both of the shafts.
Active control sticks, however, are capable of operation in a passive mode, as above described, and in an active mode that does not require automatic return to the null position. To this end, it is known to utilize centering springs that are configured to return the control stick to its null position when there is no pilot exerted force on the control stick. However, these springs are not required in the active mode, and the presence of these centering springs when operating in the active mode requires the drive motors or electro-mechanical actuators to be larger, complicates the control laws relating to control stick inertia, friction, and force discontinuities, and makes it more difficult to achieve acceptable tactile characteristics in the active mode.
Considering the foregoing, it would be desirable to provide a control stick assembly that may be continuously adjusted between first and second positions so as to operate (1) in the passive mode, utilizing a restoring system, and (2) in the active mode by neutralizing the restoring forces.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, this Background, and the appended Claims.